Determining soft data for fractional digit memory cells

Abstract

Apparatuses and methods for determining soft data for fractional digit memory cells are provided. One example apparatus can include a controller to determine states of memory cells of a group of memory cells operated as fractional digit memory cells, and determine soft data based, at least partially, on dimensions to which particular memory cells correspond with respect to the group of memory cells, determined states of the memory cells with respect to a state adjacent a state corresponding to a swapping shell, and whether a particular memory cell is a candidate for swapping.

What is claimed is:  
     
       1. An apparatus, comprising:
 a controller to:
 determine states of memory cells of a group of memory cells operated as fractional digit memory cells; and 
 determine soft data based, at least partially, on:
 dimensions to which particular memory cells correspond with respect to the group of memory cells, 
 determined states of the memory cells with respect to a state adjacent a state corresponding to a swapping shell, and 
 whether a particular memory cell is a candidate for swapping, 
 
 
 wherein the particular memory cell is one of a group of G memory cells programmed such that a combination of respective program states of the G memory cells maps to a constellation point corresponding to an N digit data value, the group of G memory cells used to store N/G digits of data per memory cell. 
 
     
     
       2. The apparatus of  claim 1 , wherein the controller determines soft data based, at least partially, on determined states of the memory cells with respect to a second highest state. 
     
     
       3. The apparatus of  claim 1 , wherein the controller determines soft data based, at least partially, on whether the particular memory cell is a candidate for swapping within a polynomial-based mapping between states and digits of data values. 
     
     
       4. The apparatus of  claim 1 , wherein the controller determines states of memory cells of the group of memory cells via a hard read, the hard read determining a sign of the soft data. 
     
     
       5. The apparatus of  claim 1 , wherein the controller determines soft data independently of the other memory cells of the group of memory cells for a memory cell corresponding to a dimension that is not a candidate for swapping. 
     
     
       6. The apparatus of  claim 5 , wherein the memory cell is not a candidate for swapping if the determined state of the memory cell is less than the second highest state. 
     
     
       7. The apparatus of  claim 5 , wherein a memory cell corresponding to a highest dimension and a memory cell corresponding to another dimension are candidates for swapping if the memory cell corresponding to the another dimension has a determined state greater than or equal to the second highest state. 
     
     
       8. The apparatus of  claim 1 , wherein the controller determines soft data via determining confidence values corresponding to a particular digit of the N digit data value. 
     
     
       9. The apparatus of  claim 8 , wherein the controller determines confidence values corresponding to the particular digit of the data value by computing a log-likelihood ratio (LLR) corresponding to the particular digit of the N-digit data value. 
     
     
       10. The apparatus of  claim 8 , wherein the constellation point is one of a number of constellation points of a constellation associated with mapping respective program state combinations of the group of memory cells to N digit data values; and
 wherein the constellation comprises a non-swapping shell and a swapping shell, the constellation points corresponding to the respective non-swapping and swapping mapping shells determined, at least partially, based on a polynomial expression of order equal to G. 
 
     
     
       11. The apparatus of  claim 1 , wherein the controller is an internal controller communicatively coupled to the array of memory cells. 
     
     
       12. The apparatus of  claim 1 , wherein the controller is an external controller communicatively coupled to a memory device, the memory device including the array of memory cells. 
     
     
       13. A method, comprising:
 determining, via a controller, states of memory cells of a group of memory cells operated as fractional digit memory cells; and 
 determining, via the controller, soft data based, at least partially, on:
 dimensions to which particular memory cells correspond with respect to the group of memory cells, 
 determined states of the memory cells with respect to a state adjacent a state that indicates a swapping shell configuration, and 
 whether a particular memory cell is a candidate for swapping, 
 wherein for a memory cell having a dimension that is not a candidate for swapping, determining soft data is based on the determined state of memory cell without consideration of the determined state of other memory of the group of memory cells, and 
 wherein determining soft data for a memory cell includes determining soft data based, at least partially, on determined states of the memory cells with respect to a state adjacent a state indicating a swapping shell correspondence configuration between memory cells and positions of digits of a data value represented by the determined state to which the respective memory cells are programmed. 
 
 
     
     
       14. The method of  claim 13 , wherein determining soft data for a memory cell that is a candidate for swapping, determining soft data is based, at least partially, on a determined state of another memory cell of the group of memory cells. 
     
     
       15. The method of  claim 14 , wherein the determined state of another memory cell of the group of memory cells is a highest dimensions of a mapping scheme. 
     
     
       16. The method of  claim 13 , wherein determining the states of the memory cells includes determining the states of the memory cells via a hard read of the memory cells, the hard read determining a sign of the soft data. 
     
     
       17. The method of  claim 13 , wherein determining soft data includes determining soft data based, at least partially, on whether the particular memory cell is a candidate for swapping within a polynomial-based mapping between states and digits of data values. 
     
     
       18. The method of  claim 13 , wherein for a memory cell corresponding to a highest dimension, determining soft data includes determining soft data based, at least partially, on a probability of the determined state of the memory cell corresponding to a highest dimension, a probability of each adjacent state to the determined state of the memory cell corresponding to a highest dimension, and a probability of determined and adjacent states of a memory cell that is a candidate for swapping with the memory cell having a dimension corresponding to the highest dimension. 
     
     
       19. The method of  claim 13 , wherein for a memory cell that is a candidate for swapping and not corresponding to a highest dimension, determining soft data includes determining soft data based, at least partially, on a probability of the determined state of the memory cell corresponding to a highest dimension and a probability of each adjacent state to the determined state of the memory cell corresponding to a highest dimension. 
     
     
       20. A method, comprising:
 determining, via a controller, states of memory cells of a group of memory cells operated as fractional digit memory cells; and 
 determining, via the controller, soft data based, at least partially, on:
 dimensions to which particular memory cells correspond with respect to the group of memory cells, 
 determined states of the memory cells with respect to a state adjacent a state that indicates a swapping shell configuration, and 
 
 
       whether a particular memory cell is a candidate for swapping,
 wherein for a memory cell corresponding to a highest dimension, determining soft data includes determining soft data based, at least partially, on a probability of the determined state of the memory cell corresponding to a highest dimension, a probability of each adjacent state to the determined state of the memory cell corresponding to a highest dimension, and a probability of determined and adjacent states of a memory cell that is a candidate for swapping with the memory cell having a dimension corresponding to the highest dimension. 
 
     
     
       21. A method, comprising:
 determining, via a controller, states of memory cells of a group of memory cells operated as fractional digit memory cells; and 
 determining, via the controller, soft data based, at least partially, on:
 dimensions to which particular memory cells correspond with respect to the group of memory cells, 
 determined states of the memory cells with respect to a state adjacent a state that indicates a swapping shell configuration, and 
 
 
       whether a particular memory cell is a candidate for swapping,
 wherein for a memory cell that is a candidate for swapping and not corresponding to a highest dimension, determining soft data includes determining soft data based, at least partially, on a probability of the determined state of the memory cell corresponding to a highest dimension and a probability of each adjacent state to the determined state of the memory cell corresponding to a highest dimension.